J/A+A/606/A107 K2/HARPS measurements for 8 stars (Oshagh+, 2017)
Understanding stellar activity-induced radial velocity jitter using
simultaneous K2 photometry and HARPS RV measurements.
Oshagh M., Santos N.C., Figueira P., Barros S.C.C., Donati J.-F.,
Adibekyan V., Faria J.P., Watson C.A., Cegla H.M., Dumusque X., Hebrard E.,
Demangeon O., Dreizler S., Boisse I., Deleuil M., Bonfils X., Pepe F.,
Udry S.
<Astron. Astrophys. 606, A107 (2017)>
=2017A&A...606A.107O 2017A&A...606A.107O (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Planets ; Radial velocities ;
Space observations
Keywords: methods: data analysis - stars: activity -
techniques: radial velocities - techniques: photometric -
methods: numerical
Abstract:
One of the best ways to improve our understanding of the stellar
activity-induced signal in radial velocity (RV) measurements is
through simultaneous high-precision photometric and RV observations.
This is of prime importance to mitigate the RV signal induced by
stellar activity and therefore unveil the presence of low-mass
exoplanets. The K2 Campaign 7 and 8 fields of view were located in the
southern hemisphere, and provided a unique opportunity to gather
unprecedented simultaneous high-precision photometric observation with
K2 and high-precision RV measurements with the HARPS spectrograph to
study the relationship between photometric variability and RV jitter.
We observed nine stars with different levels of activity, from quiet
to very active. We first probed the presence of any meaningful
relation between measured RV jitter and the simultaneous photometric
variation, and also other activity indicators (such as BIS, FWHM,
logR0'HK, and F8) by evaluating the strength and significance of the
monotonic correlation between RVs and each indicator. We found that
for the case of very active stars, strong and significant correlations
exist between almost all the observables and measured RVs; however,
when we move towards lower activity levels the correlations become
random, and we could not reach any conclusion regarding the tendency
of correlations depending on the stellar activity level. Except for
the F8 whose strong correlation with RV jitter persists over a wide
range of stellar activity level, and thus our result suggests that F8
might be a powerful proxy for activity-induced RV jitter over a wide
range of stellar activity. Moreover, we examine the capability of two
state-of-the-art modeling techniques, namely the FF' method and
SOAP2.0, to accurately predict the RV jitter amplitude using the
simultaneous photometric observation. We found that for the very
active stars both techniques can predict the amplitude of the RV
jitter reasonably well; however, at lower activity levels the FF'
method underpredicts the RV jitter amplitude.
Description:
Tables contain the radial velocity, BIS, FWHM, S-index, and logR'HK
obtained from the HARPS pipeline for 8 stars in our sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 61 8 Main stellar parameters
rv.dat 91 52 Radial velocity, BIS, FWHM, S-index, and logR'HK
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Star Star name
11- 19 I9 --- EPIC EPIC number
21- 26 A6 --- SpType MK spectral type
28- 31 I4 K Teff Effective temperature
33- 37 F5.3 Msun Mass Mass
39- 43 F5.3 Rsun Rad Radius
45- 50 F6.3 mag Vmag V magnitude
52- 56 F5.2 [-] logR'HK Stellar activity HK index
58 I1 --- NK2 Number of K2 campaign
60- 61 I2 --- NRV Number of HARPS RV observations
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Byte-by-byte Description of file: rv.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Star Star name
11- 22 F12.6 d BJD Baricentric Julian date (BJD-2400000)
24- 32 F9.5 km/s RV Radial velocity
34- 40 F7.5 km/s e_RV Uncertainty in Radial velocity
42- 49 F8.6 --- Sindex Mont Wilson S index
51- 58 F8.6 --- e_Sindex Error on Mont Wilson S index
60- 66 F7.4 [-] logR'HK Stellar activity HK index
68- 73 F6.4 [-] e_logR'HK Error on Stellar activity HK index
75- 82 F8.5 km/s FWHM FWHM of the cross-correlation function
84- 91 F8.5 km/s BIS Bisector span of the cross-correlation
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Acknowledgements:
Mahmoudreza Oshagh, moshagh(at)astro.physik.uni-goettingen.de
(End) Patricia Vannier [CDS] 02-Aug-2017